A fuller understanding of the operation of the demolition apparatus of the present invention may be achieved by studying U.S. Pat. No. 4,519,135, hereby incorporated by reference. This invention relates to a heavy duty demolition apparatus, especially adapted to be mounted on a rigid boom of a mobile vehicle and particularly adapted to be mounted on the dipper stick of an excavator, and particularly to such an apparatus with interchangeable jaws.
Heavy duty shears of the type that are powered by hydraulic cylinders are proving more and more useful in handling scrap and especially metal scrap of all sorts. Such scrap comes in many different forms, and may be in the form of pipes made of steel or soft iron or cast iron, ranging in sizes from 2 inches or smaller, and up to 8 or 10 inches in diameter or larger; structural beams such as I-beams, channels, angle beams in a large range of sizes, up to 8 or 10 inches across and larger; rods and heavy cables having diameters of 2 to 3 inches and larger, metal sheets and plates and formed metal of all sorts including wheels and automobile and truck frames, and a myriad of long and short pieces of stock and metal pieces that are cast, rolled, stamped or otherwise formed, both singly and in various types of assembly.
The prior art has included numerous shears such as that illustrated in U.S. Pat. Nos. 4,198,747; 4,188,721; 4,897,921; 4,543,719; 4,558,515 and 4,104,792. Typically, these heavy duty shears mount on the dipper stick of an excavator so that the shears may be controlled fairly well in handling various types of scrap and cutting the scrap into smaller twisted and contorted pieces and lengths as the scrap is drawn into the throat of the shear.
Typically, these shears have a fixed lower jaw and a movable upper jaw that pivots on the lower jaw, with shear blades of hardened steel on both the upper jaw and the lower jaw. The workpiece is sheared by closing the upper jaw against the lower jaw under hydraulic pressure, with the shear blades cutting the workpiece.
Shears such as these have various types of jaw attachments that may be used, for example, for cutting steel or other structural material, including concrete, or for crushing concrete, rock, or coral. Thus, it is desirable to be able to remove the jaws from the shear and replace them with jaws of another type. In the past, this has been done by detaching the jaws at the main pivot point. The main pivot pin of the jaws was slid out of the jaws and the adjacent frame plates. It was also necessary to disconnect pivot pins that attached the jaws to their hydraulic cylinders.
One problem with shears such as this is that the main pivot pin cannot be made very heavy and durable, as it must be slid out from the jaws. Also, the main pivot pin was subject to contamination when changing jaws. Furthermore, removing the main pivot pin exposed operating personnel to injury, as either the pin itself or the jaws might cause injury as the pin was removed.
There is a need for a heavy duty demolition shear with interchangeable jaw assemblies that can be easily mounted and demounted to the apparatus.